Update to mksh-45.

* [tg] Make “set -x” print the commands run in escaped form
* [tg] PS4 in dot.mkshrc is now timestamped
* [tg] The &> GNU bash I/O redir is no longer parsed in -o posix, -o sh modes,
  lksh (breaks valid scripts)
* [tg] Implement ${ …;} more efficiently (deleted-open files)
* [tg] For shf, %#s (if you can get it past GCC’s printf format attribute)
  calls print_value_quoted, ignoring field width and precision
* [tg] Catch “typeset =” (regression) with better error message
* [tg, Tonnerre Lombard] add “doch” alias to dot.mkshrc which just repeats the
  last input line with sudo(8)
* [tg] Use unsigned integers for all calculations, to avoid ISO C “Undefined
  Behaviour” (and implementation-defined behaviour) throughout (most of) the
  code; emulate signed integer arithmetics using unsigned; not-lksh only
* [tg] Emulate signed modulo naïvely, for correct sign of the result
* [tg] Add <<< and >>> for ROL and ROR (rotate left and right, respectively)
  operations, <<<= and >>> assignments; bitwise AND the RHS of a shift/rotate
  op with 31 (not for lksh)
* [tg] Remove a warning by working around a workaround found in dietlibc which
  works around a bug in broken software such as GNU tar (really!)
* [tg] Correct and simplify list and categorisation of built-in commands as
  POSIX special and “everything else” plus a flag to keep assignments
* [tg] Handle ((foo)) as “let]” internally to avoid a conflict with
  user-defined functions called let (LP#1156707)
* [tg] Clean up the code


(bsiegert)